User's Manual

CentraLite EMS
Operations, Maintenance & Service Manual
Page 27 of 31
Service Information
Troubleshooting Guide
DO NOT MOVE THERMOSTATS – All thermostats are uniquely addressed
Thermostat Problems
The following trouble shooting techniques assume that the wiring between the HVAC and the Thermostat
is correct and that the Thermostat has been controlling the HVAC properly in the past. If this is not the
case, correct any wiring problems before presuming that the Thermostat is not working properly.
Thermostat Display is Blank
The display on the Thermostat is blank. Pressing buttons on the Thermostat does not cause the backlight
to turn on or anything to display on the screen.
Remove the thermostat and either measure DC voltage between the R and C terminals(should read 24V)
or replace with temporary Thermostat. If the new Thermostat powers up properly then the old one is
defective and must be replaced. If the new Thermostat does not power up then either the HVAC unit is
not supplying power or there is a wiring issue.
Thermostat Doesn’t Control Anything
The Thermostat seems to provide no control of HVAC and temperature. Does the Thermostat screen
respond to button presses? If not then check power to the Thermostat. Check to see if the Thermostat
Mode is set to AUTO/COOL/HEAT and not OFF. If the display screen is showing a Snowflake or Flame
symbol and the Fan symbol then it is calling for COOL/HEAT/FAN and the relays are closed. Check the
wiring to the HVAC unit. You may wish to actually remove the compressor and fan wires and tie them
directly to the 24V to see if they function.
Thermostat Does Not Heat/Cool When You Move the SETPOINT Several Degrees
If the thermostat is in AUTO mode it may be switching between Heat and Cool mode. By default the
SETPOINT temperature will need to be 6 degrees. This feature is there to prevent the thermostat from
constantly changing between Heat and Cool modes when the temperature is fluctuating up and down.
Thermostat is Consistently Reading Temperature Too Low or Too High
The thermostat has a field calibration setting. The default value is zero. Ex: If the stat is reading 3
degrees too low, then change the calibration setting to 3. If the stat is reading 4 degrees to high, then
change the calibration setting to -4.